A completion using screens and a zonal isolation packer typically involves a screen assembly supported by the packer with a lateral exit between the packer and the screens for the gravel. The exiting gravel fills the annular space outside the screens while returns typically enter the screens and come into an inner string assembly that extends from the surface and through the packer to the vicinity of the screen. This inner string assembly typically has a setting tool for the packer and a crossover tool leading to a wash pipe that extends within the screen assembly. The inner string assembly is manipulated from the surface to place the crossover tool in different positions. Typically flow down the inner string can be directed into the formation for a fracturing job with the crossover tool in a position where no returns to the surface are possible. The crossover tool can be repositioned to allow gravel slurry to go down the inner string and cross over to exit out into the lower annulus below the already set packer with the carrier fluid going through the wash pipe and back through a different path in the crossover to the upper annulus above the set packer and up to the surface. After the gravel is deposited, the crossover tool is typically picked up about a meter and the remaining gravel slurry can be reversed out through clean fluid pumped down the upper annulus and into a port now in communication with the tubing that is above the packer as a result of raising the crossover.
One of the issues with gravel packing is whether the gravel distributes evenly. The gravel slurry can bridge in localized areas and cause a void around the screens that is not filled with gravel. Various techniques have been employed to prevent bridging and most involve the provision of tubes that run along the screens externally or internally in some designs that allow the gravel slurry to bypass a bridge and continue filling the annular space. These tubes are sometimes called shunt tubes because of their purpose. One example of this design is in U.S. Pat. No. 6,409,219. Fiber optic lines have been wrapped around screens but remain inactive during gravel packing. In the past these fiber optic lines are either connected to the surface when a production string tags the set packer after gravel packing when a downhole connection is made up. The downhole connection is known as a wet connect and it brings the other part of the connection to the packer so that when the production string is made up to the packer the wet connect can put the extension portion of the fiber optic line that is run along the production string in communication with the balance of the fiber optic line that was initially installed around the screen. An alternate way to do this is to connect auxiliary conduits with a wet connection and after that connection is made to pump a fiber optic cable through the conduit system that now has a portion below the packer and in the producing zone and another portion going up the side of the production tubing to the surface from the other portion of the wet connection that is delivered with the production string when tagged into the production packer. Some examples of systems that use wet connections or fiber optic lines in the ways mentioned above are U.S. Pat. Nos. 7,441,605; 7,509,000; 7,478,830; 7,475,734; 6,776,636; 6,755,253; 6,439,932; 5,294,923; US Publication 20080047703 and 20080078556.
What is needed and provided by the present invention is a way to sense the well condition during gravel packing in real time at the surface to monitor the effectiveness of the gravel pack as it occurs. This is accomplished using a sensing device that is preferably a fiber optic line that is wound around the screen assembly and passed through the packer and continued along the inner string as it is initially assembled. After the gravel pack is completed and the inner string is removed, the fiber optic line is severed preferably at a pre-designated break away connection that is sealed. The production string is then run in and using a wet connect can re-obtain the same or a discrete fiber optic line to allow monitoring to continue during production. Another aspect of the invention is the provision of a sensor. Preferably a fiber optic line is secured to the set packer at one location and can sense the relative movement of the inner string with respect to the packer. This allows for a localized measurement of the movement required downhole to get the crossover tool into its various positions without surface personnel having to guess and compensate for weight and thermal effects to determine how much surface movement will be required to get the desired movement with respect to the set packer. The present invention allows the fiber optic line to sense the relative movement in the form of stress applied to the line at various locations so as to give a real time indication at the surface that the crossover has been properly repositioned. The specific techniques of employing the fiber optic line in detecting relative movement that were disclosed in U.S. Pat. No. 7,104,331 are incorporated by reference herein as if fully set forth.
These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.